Flame resistant resin compositions

ABSTRACT

Diallyl maleate in combination with alkyl phosphates, including mixed alkyl aryl phosphates, when added to styrene-unsaturated polyester resin systems and cured with a free-radical forming initiator provides a high level of flame resistance.

This is a division, of application Ser. No. 859,838, filed Dec. 12,1977.

The present invention pertains to flame resistant styrene-unsaturatedpolyester resin systems and to a method of decreasing the flammabilityof such styrene-unsaturated polyester resins. More particularly, thisinvention is directed to styrene-unsaturated polyester resincompositions prepared by reacting a mixture of styrene-polyester resinswith diallyl maleate and an alkyl phosphate.

Organic substances containing phosphorus are well known as flameretardants for synthetic plastics, elastomers, fibers, films, etc., aswell as for many naturally occurring combustible substances. Theeffectiveness of organic phosphorus flame retardants varies widelydepending on the base substance but, in general, organic phosphorus isnot known as a highly active flame retardant element for most syntheticresin systems. Frequently, the amount needed to achieve a high level offlame resistance is excessive and the resin matrix is unable toaccommodate the high loading, that is, the resin and high level oforganic phosphorus compounds are incompatible and, in addition, alluseful mechanical properties are lost through modification with theflame retardant.

Where resin modifiers are of limited effectiveness, it is well known inthe art to seek synergists involving combinations of agents to permitthe modifiers to be empolyed at total concentrations which are less thanfor the individual agents acting alone. Although few synergisticcombinations have been definitely established among flame retardants,one couple, namely, the antimony-halogen combinations, is so widelyemployed that synergism is universally accepted even though there is nogeneral agreement as to mechanism. A similar synergism has recently beenreported for molybdenum oxide and ammonium molybdate in combination withhalogen. (D. A. Church and F. W. Moore, Plastics Engineering 31, No. 12,December 1975.) Further, molybdenum oxide combined with antimony oxidereportedly exhibits a synergism vs. the individual oxides when all arecompared in chlorine containing systems.

Synergistic effects with phosphorus are not as readily evident as withthe above metal oxides. Phosphorus plus chlorine generally yields barelyadditive effects. However, it is becoming recognized that phosphorusplus bromine produces synergistic effects in a number of systems.

Enhancement of flame retardant activity by combinations of materials isnot necessarily limited to cases in which both components exerciseactivity individually. For example, in patents to Badische Anilin andSoda-Fabrik Aktiengesellschaft (U.S. Pat. Nos. 3,420,786 and 3,457,204)certain aromatic hydrocarbons of the type2,3-dimethyl-2,3-diphenyl-butane and polymeric isopropylarylenes,respectively, are disclosed as strong activators for organic bromine inflame retardant polystyrene compositions.

Phosphoric acid esters have been used as solvents for flameproofingagents such as pentachlorophenol. The application of such solutions tocellulosic products is described in U.S. Pat. No 2,926,096.

The fire resistant properties of epoxyalkyl esters of phosphoric acidare taught in U.S. Pat. No. 3,056,806.

U.S. Pat. No. 3,511,857 discloses flame resistant polyester compositionsprepared by reacting a polybasic acid or anhydride with the freehydroxyl groups in the 1,3,2-dioxaphosphorinane ring of phosphonic acid.

Both alkyl and aryl phosphates provide a modest level of flameretardance to styrene crosslinked polyester systems. Oxygen Indexincreases at a rate of about 1.5 units per percent phosphorus present inthe complete formulation. Thus, use of organic phosphates as flameretardants as the sole active constituent has been very limited sincerelatively large quantities are required to attain even a modest levelof flame resistance. Such styrene-containing systems normally employchlorine or, more recently, bromine-containing polyesters which, whensynergized with antimony oxide, can provide a very high level of flameresistance.

In accordance with the present invention, it has now been discoveredthat phosphate esters containing at least one alkyl ester group arerendered much more effective as flame retardants for styrene crosslinkedpolyesters when used in conjunction with diallyl maleate. It isnoteworthy that diallyl maleate in the absence of alkyl phosphate causesonly a slight elevation of the Oxygen Index amounting to approximatelyone unit per ten parts of diallyl maleate added to a hundred of resin.Only alkyl phosphates are so affected although a mixed alkylarylphosphate (octyl diphenyl phosphate) gives similar results.

The flame resistance of the styrene crosslinked resin composition willvary with the structure of the alkyl phosphate. If a high level of flameresistance is desired (an Oxygen Index of 26 or higher), it is necessarythat sufficient alkyl phosphate be added to the styrene-unsaturatedpolyester to supply an effective amount, from about 0.5 weight percentto as much as about 5 weight percent of elemental phosphorus (P) basedon the weight of styrene-unsaturated polyester.

The diallyl maleate should be added to the styrene-unsaturated polyesterin amounts of about 10 to about 40 parts per hundred.

The ratio of diallyl maleate to phosphorus (P) in thestyrene-unsaturated polyester system may very within the range of fromabout 2:1 to about 50:1. Particularly preferred is a styrene-unsaturatedpolyester system containing from about 0.6 to 1.8 weight percenttriethyl phosphate and a weight ratio of diallyl maleate to elementalphosphorus in the range of from about 10:1 to 50:1. When the trialkylphosphate is tributyl phosphate, the weight percent phosphorus isdesirably about 0.8 weight percent and the ratio of diallyl phthalate tophosphorus is about 37:1.

The invention is further illustrated by the following examples in whichall quantities are given in parts by weight. The Oxygen Index reportedin the examples and tables is determined by test method D2863-76.

EXAMPLE 1

A styrene-unsaturated polyester system is prepared by dissolving a 1:1maleic-isophthalic acid ester of dipropylene glycol (manufactured andsold by the Diamond Chemical Co. under the trade name DIONE ISO 6421) inan equal weight of styrene to form a 50% solution. To 100 parts of thisstyrene-unsaturated polyester solution is added diallyl maleate andtributyl phosphate in the amounts indicated in Table I, and 3 parts perhundred of benzoyl peroxide. Each solution is agitated untilhomogeneous, then deaerated and sealed in quarter inch by eight inchglass tubes for curing. Determinations of curing characteristics byDifferential Scanning Calorimetry indicate reaction initiation for thisinitiator-resin combination occurs in the range of 70° to 75° C.Further, samples cured overnight in this temperature range show noresidual energy, i.e., all chemical reactions capable of occurring hadindeed occurred during this thermal exposure. All samples were,therefore, cured by placing the quarter inch specimens (in glass tubing)in a water bath maintained at 70° to 75° C. and heated a minimum of 16hours.

The cured specimens are relatively easily removed from the glass tubesby chilling in ice which, coupled with the contraction during curing,resulted in sufficient shrinkage to cause separation of a solid resinfrom the glass walls. Oxygen Index measurements are then made on the rodspecimens.

Table I lists the results obtained from combinations of diallyl mealeatewith various phosphate esters. Of the phosphates employed, triethylphosphate is most effective.

                  TABLE I                                                         ______________________________________                                        a. Styrene-Polyester System Containing                                        Tributyl Phosphate-Diallyl Maleate Combinations                               DAM        TBP                      Oxygen                                    (phr).sup.1                                                                              (phr)       P (%)        Index                                     ______________________________________                                        0          10          1.03         21.2                                      0          30          2.61         22.3                                      10         10          0.94         20.5                                      10         39          2.42         23.2                                      30         10          0.81         28.0                                      30         30          2.12         23.2                                      30          5          1.42         22.2                                      30         15          1.17         22.2                                      20         10          0.87         24.1                                      40         10          0.75         23.2                                      ______________________________________                                         .sup.1 (phr) = parts per hundred of styreneunsaturated polyester.        

                  TABLE I                                                         ______________________________________                                        b. Styrene-Polyester Systems Containing                                       Triethyl Phosphate-Diallyl Maleate Combinations                               DAM        TEP                      Oxygen                                    (phr).sup.1                                                                              (phr)       P (%)        Index                                     ______________________________________                                        0          0           0.0          19.0                                      10         0           0.0          19.9                                      40         0           0.0          22.2                                      0          10          1.50         23.0                                      0          40          4.71         23.3                                      10         10          1.38         24.9                                      10         40          4.40         24.9                                      40         10          1.10         32.4                                      40         40          3.67         23.2                                      40         5           0.56         25.2                                      40         15          1.60         20.2                                      30         0           0.0          23.2                                      30         5           0.61         30.4                                      30         10          1.18         26.0                                      30         15          1.71         20.5                                      20         5           0.66         20.5                                      20         10          1.27         20.5                                      20         15          1.84         28.0                                      20         20          2.36         26.0                                      ______________________________________                                         .sup.1 (phr) = parts per hundred of styreneunsaturated polyester.        

                  TABLE I                                                         ______________________________________                                        c. Styrene-Polyester Systems Containing                                       Octyl Diphenyl Phosphate-Diallyl Maleate Combination                          DAM       Sanitizer                 Oxygen                                    (phr).sup.1                                                                             141 (phr)    P (%)        Index                                     ______________________________________                                         0        10           0.76         20.5                                      30         5           0.31         21.2                                      30        10           0.59         21.2                                      30        15           0.86         21.0                                      40         5           0.29         20.2                                      40        10           0.55         28.0                                      40        15           0.81         26.0                                      ______________________________________                                        d. Isopropyl Phenyl/Phenyl Phosphate-Diallyl                                  Maleate Combinations                                                          DAM      Triaryl                    Oxygen                                    (phr)    Phosphate (phr) P (%)      Index                                     ______________________________________                                         0       10              0.68       20.5                                       0       30              1.73       22.5                                      10       10              0.63       20.5                                      10       30              1.61       21.2                                      30       10              0.54       21.0                                      30       30              1.41       21.0                                      ______________________________________                                         .sup.1 (phr) = parts per hundred of styreneunsaturated polyester.        

                  TABLE I                                                         ______________________________________                                        e. Styrene-Polyester Systems Containing                                       Combinations of Diethyl Phosphate [(EtO).sub.2 POOH]                          With Diallyl Maleate                                                          DAM        DEP                      Oxygen                                    (phr).sup.1                                                                              (phr)       P (%)        Index                                     ______________________________________                                         0          0          0            19.0                                       0         10          1.77         22.2                                       0         40          5.57         22.2                                      10         10          1.63         23.2                                      40         10          1.30         26.8                                      10         40          5.20         26.8                                      40         40          4.33         29.6                                      ______________________________________                                         .sup.1 (phr) = parts per hundred of styreneunsaturated polyester.        

What is claimed is:
 1. A flame resistant styrene-unsaturated polyesterresin composition comprising said styrene-unsaturated polyester resin incombination with diallyl maleate and about 10 parts per hundred of analkyl phosphate selected from the group consisting of octyl diphenylphosphate and tributyl phosphate; the amount of diallyl maleate presentin said styrene-unsaturated polyester resin being about 30 parts perhundred when tributyl phosphate is present in said composition and about40 parts per hundred where octyl diphenyl phosphate is present in saidcomposition.
 2. The flame resistant styrene-unsaturated polyester resincomposition of claim 1 comprising said styrene-unsaturated polyesterresin in combination with about 40 parts per hundred of diallyl maleateand about 10 parts per hundred of octyl diphenyl phosphate.
 3. The flameresistant styrene-unsaturated polyester resin composition of claim 1comprising said styrene-unsaturated polyester resin in combination withabout 30 parts per hundred of diallyl maleate and about 10 parts perhundred of tributyl phosphate.
 4. The method of improving the flameresistance of a styrene-unsaturated polyester resin which comprisesadding to said styrene-unsaturated polyester resin, prior topolymerization diallyl maleate and about 10 parts per hundred of analkyl phosphate selected from the group consisting of octyl diphenylphosphate and tributyl phosphate; the amount of diallyl maleate presentin said styrene-unsaturated polyester resin being about 30 parts perhundred when tributyl phosphate is present in said composition and about40 parts per hundred when octyl diphenyl phosphate is present in saidcomposition; and heating the mixture to polymerization temperature inthe presence of a catalyst.
 5. The method of claim 4 wherein there isadded to said styrene-unsaturated polyester resin, prior topolymerization about 40 parts per hundred of diallyl maleate and about10 parts per hundred of octyl diphenyl phosphate.
 6. The method of claim4 wherein there is added to said styrene-unsaturated polyester resin,prior to polymerization about 30 parts per hundred of diallyl maleateand about 10 parts per hundred of tributyl phosphate.